• When the Twins let half of last season's bullpen leave via free agency and chose to replace them with in-house options the hope was that several young relievers would step up to claim long-term roles. That not happening has played a big part in the team's overall struggles, but the Twins have had one reliever step up in Glen Perkins. He fell out of favor due to injuries and poor work as a starter, spending last year at Triple-A, but now looks like a new man.

Getting healthy and moving to the bullpen full time has allowed Perkins to add velocity, with his average fastball clocking in at 92.7 miles per hour compared to 90.6 mph prior to this year, and the results are similarly encouraging. After impressively getting four key outs against the A's in last night's 4-3 win Perkins now has a 0.82 ERA and 22-to-8 strikeout-to-walk ratio in 22 innings, holding opponents to a .230 average and zero homers. He's been a rare bright spot.

• There's still no timetable for Joe Mauer's return, but he took a significant step in his recovery by heading to extended spring training to rehab alongside Tsuyoshi Nishioka. Jim Souhan of the Minneapolis Star Tribune interviewed Mauer recently for a column and speculates that what has "kept him from providing more clarity" about his ongoing health status "is that he doesn't want to blame anyone else for his lack of progress." Here's a little more from Souhan:

My guess is that he feels he didn't receive proper guidance or advice at some point during his surgery/rehab process, but he's too polite to call anyone out. That would explain why he took an extra visit to the Mayo Clinic to get checked out even after the Twins gave him medical clearance to play.

What I took away from my talks with Mauer is that he hates being portrayed as a slacker, and is desperate to get back on the field, but fears that if he rushes the process he'll be lost for the season or do himself permanent harm.

All of which seems to fit with Mauer and team trainer Rick McWaneboth admitting that he was not physically ready to begin the season on the active roster following knee surgery.

• They'll still be nowhere near full strength, but the Twins will get a little healthier Monday with Jim Thome and Jason Repkoexpected to return from the disabled list. Both players will need to avoid setbacks while playing minor-league rehab games until then, as Repko has been out since May 2 with a strained right quadriceps and Thome has been hampered by a strained left oblique since April 24.

• Repko's return will push Ben Revere back to Triple-A, while Thome's return forces the Twins to trim the pitching staff from 12 to 11 or demote Luke Hughes, Alexi Casilla, or Matt Tolbert from the infield mix. Casilla is out of minor-league options and appears to have secured the second base job with four straight starts there. Hughes has more starts than Tolbert recently, but just like in spring training Tolbert's ability to play shortstop likely gives him the edge.

• Delmon Youngmissed back-to-back starts to "clear his head" after coming off the DL with 10 strikeouts in 16 at-bats and pathetic effort defensively, which allowed Revere to show off his range last night with a sprinting catch in Oakland's expansive foul territory on a fly ball that would've landed 10 feet from Young. Revere's arm is awful and his upside is limited offensively, but using him in left field next season would completely change the Twins' outfield defense.

• Jose Mijares heading to the disabled list with a strained elbow might explain his 11 walks in 12 innings after issuing a total of 32 walks in his first 105 innings. In addition to placing Mijares on the shelf the Twins also optioned Jim Hoey back to Triple-A after a month-long bullpen stint in which his mid-90s fastball and poor control were both as advertised and opponents batted .375/.432/.725 off him in 10 games. Oddly, six of his 10 outings came in high-leverage spots.

• To replace Mijares and Hoey on the roster and in the bullpen the Twins brought up Anthony Swarzak and Phil Dumatrait from Triple-A. This is Swarzak's second stint with the Twins this year and he's been on the 40-man roster since 2009, but Dumatrait's call-up required clearing a spot first and they did so by designating Steve Holm for assignment. As a replacement-level catcher Holm will likely pass through waivers unclaimed and the Twins soured on him anyway.

• At first glace Dumatrait might look like an intriguing call-up based on his 1.15 ERA at Triple-A, but don't be fooled. His shiny ERA is the result of just 16 innings and came along with an awful 12-to-11 strikeout-to-walk ratio. He had a 6.13 ERA with more walks (55) than strikeouts (46) in 104 innings as a starter at Triple-A last year and has a 7.06 ERA with almost as many walks (65) as strikeouts (68) in 110 innings in the majors. Oh, and he's 29 years old.

• Swarzak once ranked among the Twins' top pitching prospects, but got knocked around in 12 starts as a 23-year-old rookie in 2009 and then went 5-12 with a 6.21 ERA in 22 starts back at Triple-A last year. He's been much better at Rochester this year with a 3.90 ERA and 25/7 K/BB ratio in 32 innings, but as a 25-year-old with a 4.32 ERA and 165/80 K/BB ratio in 269 innings spread over parts of four seasons at Triple-A he projects as a marginal big leaguer.

• There hasn't been any talk of Justin Morneau's post-concussion symptoms returning, but Sid Hartman of the Minneapolis Star Tribunewrites: "I believe [Morneau] is playing daily despite being more injured than some of the Twins players on the disabled list." Whether or not that's accurate, Morneau has yet to get on track offensively and Parker Hageman at Over The Baggy broke down his swing mechanics to find that they've changed for the worse.

• Sadly the Twins' injuries aren't limited to the big-league roster. Oswaldo Arcia, who ranked 12th on my list of the Twins' top prospects coming into the year and was off to a tremendous start at low Single-A, is expected to miss two months following elbow surgery.

• Alex Wimmers isn't hurt, but what ails him may be even worse. He had a disastrous season debut at high Single-A, walking all six batters he faced and uncorking several wild pitches, at which point the Twins removed Wimmers from Fort Myers' rotation and sent him to extended spring training. Seth Stohsreports that Wimmers walked five batters over three innings in his first start there, so the 2010 first-round pick is going down the Rick Ankiel/Steve Blass path.

• Carl Pavano turned in a solid start against the A's last night, allowing just one earned run in seven innings, but once again struggled to miss bats and has now managed to strike out just three of the last 105 batters he's faced. Not a very encouraging sign for a 35-year-old pitcher under contract for $8.5 million next season.

• Darren Rovell of CNBC notes that Francisco Liriano's no-hitter earned him at least $22,000 thanks to an autograph-signing deal. Meanwhile, his nine-strikeout, one-walk outing Tuesday night against the Mariners was more impressive than the two-strikeout, six-walk no-hitter.

• Alexi Casilla's ill-conceived reign as the Twins' starting shortstop lasted all of a month, as he played his way out of the job by hitting just .190/.257/.286 with predictably spotty defense at a position where he lacked both the skills and experience to succeed. Trevor Plouffe has now taken over at shortstop, earning a call-up by shaking off a dreadful spring training to start well at Triple-A. That leaves Casilla as the primary second baseman, with Ron Gardenhiresaying:

I talked with Alexi about it. I asked him about second base and he said it's easier. We'll see if it's easier. I know he's always more comfortable over there too. I think he's trying to do a whole heck of a lot. At second base maybe he'll be able to relax a little bit more and not rush things.

Casilla needing to relax and get comfortable has been repeated like a manta since his debut in 2006, along with talk of supposed upside. At this point, however, it might be time to conclude that Casilla just isn't very good. He'll be 27 years old in July and has 1,200 plate appearances in the majors, so Casilla is neither young nor inexperienced. Defensively he's overmatched at shortstop and merely decent at second base, and he's a career .244/.301/.321 hitter.

Even his best raw tools more often than not go to waste. Casilla has a strong arm, but the big windup and shaky accuracy mean he can't be counted on to make routine plays. He has great speed and is a remarkably efficient base-stealer, yet has a grand total of just 37 steals in 338 games. Casilla is out of minor-league options and can't be sent to Triple-A without first passing through waivers, but the risk of losing him should no longer be part of the decision-making.

• There's no immediate reason to cut bait on Casilla, but if Plouffe is performing well enough to keep a starting job by the time Tsuyoshi Nishioka is ready to return from his fractured fibula in a couple weeks keeping Casilla around would likely mean demoting Matt Tolbert to Triple-A or reducing the pitching staff from 12 to 11. It's difficult to imagine Ron Gardenhire being in favor of either option, so Casilla may truly be playing for his Twins future right now.

Of course, Plouffe having a strong grip on the job in 2-3 weeks is hardly assured. According to Gardenhire the coaching staff at Rochester praised Plouffe's defense and he hit .282/.344/.590 in 21 games there, but that brings his career mark at Triple-A up to just .255/.306/.430 in 307 games and his shortstop defense received mixed reviews long before the error-filled showing this spring. He ranked 32nd on my list of the Twins' top prospects coming into the season.

Plouffe's flaws may be different and less familiar than Casilla's flaws, but aren't necessarily any less abundant and a 25-year-old with a non-elite glove and .306 on-base percentage in 1,300 plate appearances at Triple-A isn't significantly more likely to impress as an everyday shortstop than Casilla or Tolbert. Plouffe is worth a look at shortstop and so is Nishioka once he returns, but this may not be a problem that can be solved by shuffling a deck full of the same cards.

• On the other hand, injuries to Delmon Young and Jim Thome forced the Twins to call up Ben Revere and Rene Tosoni, both of whom project as more likely long-term starters than Plouffe. Tosoni got the nod with Young out by virtue of his better start at Triple-A, but then Revere was called up anyway once Thome and Jason Repko went on the shelf last week and now they're splitting time in left field despite the two left-handed hitters not forming a natural platoon.

Thome, Jason Kubel, and Michael Cuddyer are impending free agents, so it's possible Revere and Tosoni will be two-thirds of the starting outfield next season along with Denard Span. For now they're just keeping the roster spots warm with Young seemingly close to returning and both Thome and Repko also due back before the end of the month. Revere seems more likely to stick once Young returns because he fills Repko's role as the backup center fielder.

• When the Twins claimed Dusty Hughesoff waivers from the Royals in January they talked up his nice-looking ERA and the fact that left-handed hitters like Mauer and Span raved about his stuff after facing him. Ignored in all that were mediocre secondary numbers last season and an underwhelming track record in the minors, and sure enough Hughes was demoted to Triple-A after posting a 10.13 ERA in 12 appearances while opponents batted .356/.434/.622 off him.

Meanwhile, the player dropped from the 40-man roster to make room for Hughes three months ago, Rob Delaney, was called up by the Rays yesterday after posting a 1.50 ERA and 19-to-5 strikeout-to-walk ratio in 18 innings at Triple-A. Delaney won't necessarily stick in Tampa Bay and Hughes might thrive if given another shot in Minnesota, but so far the reliever swap based on ERA and hitter reviews rather than secondary stats and track records looks like a mistake.

• Last month when Joe Mauer was placed on the disabled list the Twins called up Steve Holm from Triple-A to serve as Drew Butera's backup and Gardenhire said things like "he can swing it" and "we liked him in spring training." Holm's track record said otherwise, as the 31-year-old career minor leaguer had hit just .250/.334/.379 at Triple-A. Holm predictably struggled, going 2-for-17 at the plate and 0-for-5 throwing out runners before being demoted back to Triple-A.

Holm is the definition of a replacement-level catcher, so there's no reason to fault the Twins for dropping him, but the process by which he so quickly fell out of favor is curious given that the Rochester call-up taking his job, Rene Rivera, is every bit as much a replacement-level catcher with a decade in the minors and an even less impressive track record. Why make that switch just weeks after calling up Holm over Rivera in the first place? Here's what Gardenhire said:

Just trying to mix it up. Don't want to sit here and get complacent. I hope these guys understand we're not afraid to move people around. It's just a change. Holm hadn't been swinging great. They told me Rivera was hitting balls right on the button. Terry Ryan had been watching him the last few days. He can run into a ball, and we need somebody who can run into the ball.

Presumably the Twins scouted both players before signing them as free agents this winter and then formed further opinions about them during spring training. Last month that meant calling up Holm over Rivera, yet three weeks and just 18 plate appearances later they reversed that decision because Holm "hadn't been swinging great" and Gardenhire got a report that Rivera "was hitting balls right on the button." Sounds a lot like his quotes about Holm last month.

Terry Ryan must have watched Rivera on a rare good day, because he hit just .200/.250/.333 at Rochester before the call-up. Beyond that, the notion that Rivera "can run into a ball and we need somebody who can run into the ball" is being awfully kind to a career .245 hitter with a .405 slugging percentage in parts of seven years at Triple-A. Decisions don't get less important than "Holm or Rivera?" but the decision-making process in this case fascinates me.

• As if that wasn't already too much talk about replacement-level backup catchers ... When the Holm-for-Rivera swap was announced quite a few people e-mailed and tweeted me wondering why 2007 eighth-round pick Danny Lehmann didn't get the nod instead. My assumption is that those people looked at his .325 batting average in a dozen games this season rather than his ugly .239/.318/.312 career line in five seasons. Lehmann is homegrown, but that's about it.

• Francisco Liriano's no-hitter obviously quieted Gardenhire's talk of Kevin Slowey coming off the disabled list to replace him in the rotation, so instead Slowey rejoined the bullpen with a start-length relief outing after Saturday's rain delay. Slowey began the season in a secondary setup role, but with the bullpen hierarchy changing dramatically in the month he missed it'll be interesting to see if he reclaims the high-leverage role that he's capable of thriving in.

For a brief time last night Joe Nathan and Matt Capps both blowing saves against the Rays to waste Carl Pavano's eight shutout inningsseemed like a pretty big deal. And then the Twins announced after the loss that Joe Mauer has been placed on the disabled list with what they are calling bilateral leg weakness. Details on the injury are somewhat scarce for now, but he'll be examined by a specialist in Baltimore early next week and it certainly doesn't sound good.

Mauer, who clearly hadn't looked like his usual self while hitting .235/.289/.265 in nine games, has apparently been experiencing significant soreness in his hip and shoulder in addition to his surgically repaired knee. According to manager Ron Gardenhire "compensating for weakness in his upper leg ... is causing a lot of other problems" and after initially trying to play through the pain Mauer asked out of the lineup last week before missing the past two games.

From asking around and doing a bit of Google digging there are some extremely scary aspects of bilateral leg weakness, but it doesn't make much sense to speculate on anything until he's seen the specialist next week and more details are known. However, it certainly doesn't sound like Mauer will be back from the disabled list anytime soon and unfortunately after trading both Wilson Ramos and Jose Morales the Twins are exceptionally short on catching depth.

Drew Butera will take over as the primary catcher and the Twins have called up minor-league veteran Steve Holm from Rochester to serve as his backup. Butera is very strong defensively and Holm had a couple brief stints in the majors with the Giants in addition to 11 seasons in the minors, but there isn't a worse catching duo in the big leagues and asking them to replace the best catcher in baseball represents just about the largest possible dropoff.

Butera has hit .194/.230/.284 in the majors after batting .214/.296/.317 in the minors, making him perhaps MLB's worst hitter, and Holm has hit just .249/.330/.380 in 170 games at Triple-A. Even if they collectively perform relatively well the Butera-Holm combo is likely at least 60 runs worse offensively per year than Mauer. Or at least a reasonably healthy Mauer, which despite the frequent criticisms of his durability is mostly what the Twins have gotten.

Since missing most of his 2004 rookie season after knee surgery Mauer has played an average of 134 games per year and his 3,494 plate appearances during that time lead all MLB catchers. He also leads all catchers in plate appearances since 2006, since 2007, and since 2008. Not all of those plate appearances have come at catcher, but he's ranked among the league's top five in innings caught in four of the past five seasons.

Mauer has seen 12 percent of his career action elsewhere, but that's common for good-hitting catchers in the AL. For comparison, Victor Martinez is at 12 percent and Jorge Posada is at 10 percent. Mauer's overall lack of durability has largely been overstated because every injury is a huge story and many people don't appreciate that standard catcher workloads involve taking off more games than other positions. Of course, none of that feels like it matters right now.